Q. 5 cells, each of emf $0.2V$ and internal resistance $1\Omega$ are connected to an external circuit of resistance of $10\Omega.$ Find the current through external circuit
A) $\frac{1}{2.5}A$
B) $\frac{1}{10}A$
C) $\frac{1}{15}A$
D) $\frac{1}{2}A$
Explanation
(c) [image:3_image172.emf]
Here, emf of each cell, $\varepsilon = 0.2V$
Internal resistance of each cell, $r = 1\Omega$
External resistance, $R = 10\Omega$
The total emf of 5 cells $= 5\varepsilon = 5(0.2)V = 1V$
Total internal resistance of 5 cells $= 5r = 5(1)\Omega = 5\Omega$
Total resistance of the circuit $= R + 5r = 10 + 5 = 15\Omega$
The current in the external circuit,
$I = \frac{5\varepsilon}{R + 5r} = \frac{1V}{15\Omega} = \frac{1}{15}A$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.